Here is the full list of all 45 The Forest achievements. It takes around 50-60 hours to unlock all of the achievements on Windows.
Revive 10 co-op players
Pass 50,000 steps
Kill all animal types and display heads
Find all missing passengers
Explore all caves
Craft all items
Share a weapon in MP
Share a food or drink item in MP
Cut down 1000 trees
Kill shark. Alone in Single Player or together in Multiplayer.
Play through entire game without killing or eating animals. Alone in Single Player or together in Multiplayer.
Collect all robot pieces
Catch fish with a trap. Alone in Single Player or together in Multiplayer.
Kill 6 or more fish with a stick of dynamite. Alone in Single Player or together in Multiplayer.
Build a super long wall
Craft 10 medicine items
Eat an entire family
Grow all plant types
Eat all mushroom types
Finish Game
Knock down 6 or more trees with 1 explosive. Alone in Single Player or together in Multiplayer.
Collect all cassette tapes!
Set off 20 bombs
In Single Player, don't kill any cannibals for more than 10 days in a row
Chop up 50 bodies
Use the compass
In Single Player, kill 100 cannibals
Cut down 100 trees
Sleep on yacht
Revive one co-op player
Sleep with another player (group sleep)
Killed downed enemy with rock
Kill bird with arrow
Eat an enemy
Make and wear stealth armour
Repair a shelter
Kill a bunny. Alone in Single Player or together in Multiplayer.
Survive 5 nights
Survive 1 night